Gram positive bacteria contain lipoteichoic acid and have a membrane system consisting of a plasma membrane and mesosomes. The aim of this project is to correlate membrane structure with function using Staphylococcus aureus as the model test system. The major emphasis of this study is to ascertain the function (or functions) of mesosomes which contain the lipoteichoic acid present in the cell. The topics of present interest are: distribution of lipoteichoic acid during growth; isolation, purification and characterization of lipoteichoic acid; and immunochemical localization of lipoteichoic acid.